I've just taken delivery of a PS DirectStream Jnr that initially will replace my Grace m902 DAC/Pre-amp, until I can afford to buy a higher spec. Mac Mini and run a slick Roon core to feed the DS Jnr through its Bridge.

Does anybody have advice about the best ways of feeding the DS Jnr from the Sonos and from the Transporter? Optical to avoid electrical interference? Co-ax. for lower jitter, but does that matter as the DS Jnr is so good at jitter rejection? AES/EBU from the Transporter to the DS Jnr? In the end I'll go for what sounds best but if anybody has advice about what NOT to bother with that might save me some time!

I’d encourage you to try optical for the source you think you’ll listen to the most. Zero electrical noise is a big win and the DirectStream is incredibly good at eliminating the kind of jitter that Toslink is known for.

If you’ve got a proper balanced, differential XLR cable then AES/EBU would also be a good option. It will electrically link your DAC and your transporter but at least it won’t pick up radiated intereference on the path between the two.

I haven’t had good results with optical, though some swear by it, including the guy who modded my Mini (same guy that did Paul’s). I got one of the real glass (not plastic) cables he suggested. But it still sounds to me like it’s connecting two ten-cent converters. Very “clean and crystal clear” but tilted to the top end to my ears.